Sensing and control system

ABSTRACT

A sensing and control system for controlling operation of a machine comprises a timer which is arranged to modify the action of the machine after the elapse of a preset time interval from the occurrence of a first given operating condition of the machine if a second given operating condition does not occur within the interval timed. If the second condition occurs within the interval timed the modifying action of the timer is disabled.

United States Patent [191 [111 3,786,470 Greenhill Jan. 15, 1974 SENSINGAND'CONTROL SYSTEM Primary Examiner-Donald J. Yusko [76] Inventor: DerekHoward Greenhill, Arthur St., Aswan swam Redditch, EnglandAttorney-Marshall 8L Yeastmg [22] Filed: July 25, 1972 211 Appl. No.:274,867' [57] ABSTRACT A sensing and control system for controllingoperation [52] us Cl 340/267 R 226/100 340/282 of a machine comprises atimer which is arranged to [51] Int G68!) 21/00 modify the action of themachine after the elapse of a [581 i 282 213 preset time interval fromthe occurrence of a first H00 200261 61 given operating condition of themachine if a second given operating condition does not occur within the[56] References Cited interval timed. If the second condition occurswithin the interval timed the modifying action of the timer is UNITEDSTATES PATENTS disabled 2,076,236 4/1937 Holloway 226/100 6 Claims, 3Drawing Figures PATENTEDJAN 1 5 m4 sum 1 [1F 2 Fig.

Fig.3.

SENSING AND CONTROL SYSTEM BACKGROUND OF THE INVENTION This inventionrelates to a sensing and control system for use in controlling theoperation of a machine in which a succession of operations (orrepetition of the same operation) is carried out each within apredetermined time period and it is desired to modify operation of themachine, including stopping the machine or at least its feed mechanismand possibly provide audible and/or visual warning, if any operation (orseries thereof) is not carried out within the time allotted for it. Theinvention is particularly applicable to spring coiling machines in whicha continuous length of coil spring is formed from wire and severed atpredetermined intervals. It may however have other applications, as forexample to wire forming or straightening machines. i

In machinessuch as spring coiling machines in which successivepredetermined lengths of material are severed from a continuous length,a number of faults can occur which can lead to great incovenience andpossibly damage to the machine if the latter is allowed to continueinfaulty condition. Examples of such faults are (a) wire breakage, (b)exhaustion of wire supply, failure of wire feed and (d) failure of thecutting mechanism.

An object of the invention is to provide a sensing and control systemfor use with machines of the above kind whereby such faults as well asthe severing of incorrect lengths of material are sensed and themachine, or a part of its mechanism, is automatically stopped or itsperformance otherwise modified in response to sensing of a fault.

SUMMARY or THE'INVENTION In its broadest aspect the invention resides ina sensing and control system for controlling the operation of a machinecomprising a timer arranged to actuate means to modify the action of themachine after the elapse of a predetermined time period from theoccurrence of afirst given operating condition of the machine if asecond given operating. condition of the machine does not occurbefore-said time period elapses, and including sensing means fordetecting the occurrence of said second operating condition andpreventing actuation of said means by the timer when said secondcondition is detected during said predetermined time period. 1

More specifically, theinvention resides in a sensing and control systemfor controlling the operation of a machine comprising first and secondtimers arranged to actuate means for modifying the action of themachine, the first timer being arranged to actuate said means after theelapse of a first predetermined time period from the occurrence of afirst given operating condition of the machine if a second givenoperating condition of the machine does not occur before said first timeperiod elapses, and the second timer being arranged to actuate saidmeans after the elapse of a second predetermined time period from theoccurrence of said second given operating condition if a third givenoperating condition of the machine does not occur before said secondtime period elapses, andsensing means for detecting the occurrence ofsaid second and third operating conditions and preventing actuation ofsaid means by the first timer when said second condition occurs withinsaid first predetermined time period and by the second timer when saidthird condition occurs within said second predetermined time period.

It will be understood that the expression the occurrence of a givenoperating condition includes the failure of the machine to attain aparticular operating condition or to perform an operation as well as theobtaining of an operating condition or completion of an operation.

In a convenient arrangement, particularly applicable to a spring coilingmachine, two electrically operated timers are provided, onebeingarranged for actuation by contact with a sensing element with theend of a workpiece (in this case a coil spring) fed by the machine andto modify operation of the machine if such contact is maintained forlonger than a predetermined period, the other being arranged'to modifyoperation of the machine if no contact is made with the sensing meansafter a predetermined period has elasped. The timers may conveniently bearranged to interrupt the machine feed at the end of said predeterminedperiods. Operation of the timers is effected through an electricalcircuit completed by said contact of the sensing element and formedspring.

Thus, one timer guards against occurrence of faults (a) to (c) and theother against fault (d). The timers also guard against-excessively longor short springs being formed.

A similar arrangement may be applied to other kinds of machines in whichlengths of material are severed in succession from a continuous length,such as wire forming and straightening machines.

BRIEF DESCRIPTION OF THE DRAWINGS FIG; 1 is a circuit diagram of asensing and control system according to the invention;

FIG. 2 is a circuit diagram of a modified form of the sensing andcontrol system of FIG. I; and

FIG. 3 is a diagrammatic view of part of a machine incorporating thesystem of either FIG. 1 or FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS I Referring to FIG. 3, amachine, for example, a conventional helical spring coiling machine,designated generally by reference numeral 10 continuously feeds acontinuous length of a workpiece 11, such as a coil spring or wire, pastan unshown severing device, where discrete lengths are severed by thesevering mechanism after the normal time taken for feeding apredetermined length of workpiece has expired. The circuit of FIG. 1, orFIG. 2, controls feeding of the workpiece l 1.

The circuit of .FIG. 2 incorporates a power pack comprising atransformer 12, the primary 12a of which is connected to a 400/240 voltsupply through a ganged switch S and the secondarylZb of which isconnected to a diode bridge rectifier 14. Numeral l5 depicts a power onindicator lamp connected across the secondary 12b. The rectified supplyis smoothed by a capacitor 16.

The circuit also includes a pair of timers T1 and T2, the timer Tl beingconnected across the low tension side (conveniently 12 volts) of thepower supply through a normally closed contact 17d of a relay 17connected in parallel with timer T2 and in series with a normally openswitch 18a of a relay 18.The relay [8 is connected to the collector of atransistor l9. The circuit of FIG. 2 additionally incorporates a furtherrelay connected to the collector of a transistor 21.

The machine carries three electrical contacts 22, 23 and 24. The contact22 is carried by the main body of the machine whilst the contact 23 iscarried by the spindle of a micrometer, the barrel 26 of'which isinsulated electrically. The micrometer -is mounted by a member 27 whichis adjustable axially of the direction of feed movement of the workpiece11, the spindle of micrometer 25 being co-aitial with said direction offeed movement. The member 27 also mounts a resilient blade 28 whichprojects into the. path of feed movement of the workpiece 11 and thecontact 24 is secured to the blade 28.

When the blade 28 contacts the workpiece ll, electrical continuity isestablished between contacts 22 and 24 and, referring to FIGS. 1 and 2,the transistor 19 conducts in response to suchcontact. Similarly, whenthe blade 28 contacts the tip of the spindle of the micrometer 25,electrical continuity is established 'between contacts 24 and 23 andtransistor 21 of FIG. 2 conducts when this circuit is used instead ofthat of FIG. 1.

Feed movement of the workpiece 11 occurs in response to closing of theswitch S and simultaneously timer Tl begins its timing cycle the periodof which is selected so as to be slightly in excess of the normal timerequired for a predetermined length of workpiece 1 1 to be fed, towardsthe blade 28. When the normal time for feeding said predetermined lengthof workpiece towards the blade 28 expires the severing mechanism of themachine is rendered operative to sever the length of workpiece fed. Theposition of the blade 28, which may be adjusted by adjusting theposition of member 27, is set in accordance with the predeterminedlength of workpiece 11 to be fed by the machine. As the tip of theworkpiece 11 contacts blade 28, electrical continuity is establishedbetween contacts 22 and 24 causing transistor 19 to conduct. Relay [8 isthus energised to close its associated contact 18a and energise relayl7.

Normally closed contact 17a opens and timing by timer T1 is terminatedand the timer Tl then automatically re-sets to its zero state. TimerT2starts to time as soon as contact 18a closes and is set totime outafter a period just later than thegnormal time required for the severingmechanism to -sever the length of workpiece fed. When the spring hasbeen severed, it falls away from the blade 28 and the circuit acrossterminals 22 and 24 is broken andconsequently relay contact 18a opens tostop timer T2 when automatically re-sets to its zero state.

Timers TI and T2 are associated with internal contacts of the machinewhich operate, in response to timing out of each timer, to interrupt thesupply of power to the machine feed motor for example, or otherwise tostop the feed, and possibly also to actuate an audible or visual alarm.thus, if the workpiece fed towards blade 28 does not make contacttherewith before timer Tl times out, the feed movement will beinterrupted by closure of said internal contacts. If however contactbetween blade 28' and the workpiece is made within the period timed bytimer Tl, timer T2 is rendered operative and will cause closure of saidinternal contacts of the machine if the severed length of workpiece doesnot fall away from the blade 28 within the period the timer T2 is settotime.

Thus, the circuit of FIG. 1 guards against the occurrence of certainfaults such as (a) breakage of the workpiece, (b) exhaustion of theworkpiece supply, (0) failure of workpiece feed and (d) failure of thesevering mechanism. Timer Tl guards against faults (a) to (0) Whilsttimer T2 guards against fault (d).

An additional safeguard against failure, or retarded operation of thesevering mechanism is provided by the circuit of FIG. 2. When the lengthof workpiece ll contacts the blade 28, in order to maintain continuousoperation of the machine, the feed movement is not terminated andconsequently the feed movement continues whilst the severing mechanismis, or should be, operative. In the normal course of events, thesevering mechanism is actuated immediately in response to expiration ofthe normal time required to feed a predetermined length of the workpiece11 and conseqeuntly no substantial flexing of the blade 28 occurs if theworkpiece fed is of the predetermined length. However, if operation ofthe severing mechanism is retarded or malfunctions or if the length ofworkpiece fed exceeds said predetermined length, the blade 28 will beflexed in a direction towards the spindle of the micrometer 25. Bysetting the axial spacing between the unflexed blade 28 and the tip ofthe spindle of the micrometer 25, an upper limit can be set to thelength of severed workpiece that is acceptable and if circumstancesarise in which this upper limit tends to be exceeded, for example undulyretarded operation of the severing mechanism or excessive feed of theworkpiece, the blade 28 will be flexed by'the workpiece into contactwith the spindle of the micrometer thereby establishing electricalcontinuity between contacts 23 and 24. Such contact will energise relay20 which may be arranged to close said internal contacts of the machineand thereby terminate feed movement and/or actuate an alarm andadditionally open contact 18a to stop operation of timer T2.

Thus, the spacing between the blade 28, in its unflexed position and theinitial feed point of the leading end of the workpiece upon closure ofswitch 8. or after a previous severing operation, determines the minimum acceptable length of workpiece severed by the machine whilst thespacing between said initial feed point and the tip of the spindle ofmicrometer 25 deter mines the maximum acceptable length of workpiecethat may be severed by the machine. 1

As described, the timer T1 is set to time out just after the normal timefor feeding a predetermined length of workpiece expires and if thelength fed in this normal time is not sufficient to contact blade 28, ashort length is severed and the machine feed is stopped;

.However, the timer Tl may be set to time out in a period such that twoor more short lengths may be severed before it operates to close theinternal contacts of the machine feed.

I claim:

1. A sensing and control system for controlling the operation of amachine comprising first and second timers arranged to actuate means formodifying the action of the machine, the first timer being arranged toactuate said means after the elapse of a first predetermined time periodfrom the occurrence of a first given operating condition of the machineif a second given operating condition of the machine does not occurbefore said first time period elapses, and the second timer beingarranged to actuate said means after the elapse of a secondpredetermined timer period from the occurrence of said second givenoperating condition if a third given operating condition of the machinedoes not occur before said second time period elapses, and sensing meansfor detecting the occurrence of said second and third operatingconditions and preventing actuation of said means by the first timerwhen said second condition occurs within said first predetermined timeperiod and by the second timer when said third condition occurs withinsaid second predetermined time period.

2. A system according to claim 1 wherein the first timer is arranged tostart timing in response to initiation of feeding movement of aworkpiece by the machine and timing by the first timer is arrested inresponse to contact of said workpiece with a sensing element of thesensing means. I

3. A system according to claim 1 wherein the second timer is arranged tostart timing in response to contact of a workpiece fed by the machinewith a sensing element of the sensing means and timing by the secondtimer is arrested in response to disengagement of said workpiece fromsaid sensing element.

4. A system according to claim 1 wherein said machine includes means forfeeding a workpiece through a predetermined distance within said firstpredetermined time period and means for performing an operation of saidworkpiece on completion of feeding thereof through said predetermineddistance, completion of feeding of said workpiece through saidpredetermined distance constituting said second given operatingcondition of the machine, said system further including further sensingmeans for sensing feed movement of said workpiece in excess of saidpredetermined distance by a pre-selected amount and actuating saidmodifying means in response to sensing of said excess feed movement.

S. A system according to claim 1 wherein the modifying means actuated byeach timer interrupts the machine feed at the end of the period at whichthe timer is set to time.

6. A sensing and control system for controlling the operation of amachine comprising a timer arranged to actuate means to modify theaction of the machine after the elapse of a predetermined time periodfrom the occurrence of a first given operating condition of the machineif a second given operating condition of the machine does not occurbefore said time period elapses, including sensing means for detectingthe occurrence of said second operating condition and preventingactuation of said modifying means by the timer when said secondcondition is detected during said predetermined time period, saidmachine including means for feeding a workpiece through a predetermineddistance within said predetermined time period, completion of feeding ofsaid workpiece through said predetermined distance constituting saidsecond given operating condition of the machine, said system furtherincluding sensing means for sensing feed movement of said workpiece inexcess of said predetermined distance by a pre-selected amount andactuating said modifying means in response to sensing of said excessmovement.

1. A sensing and control system for controlling the operation of amachine comprising first and second timers arranged to actuate means formodifying the action of the machine, the first timer being arranged toactuate said means after the elapse of a first predetermined time periodfrom the occurrence of a first given operating condition of the machineif a second given operating condition of the machine does not occurbefore said first time period elapses, and the second timer beingarranged to actuate said means after the elapse of a secondpredetermined timer period from the occurrence of said second givenoperating condition if a third given operating condition of the machinedoes not occur before said second time period elapses, and sensing meansfor detecting the occurrence of said second and third operatingconditions and preventing actuation of said means by the first timerwhen said second condition occurs within said first predetermined timeperiod and by the second timer when said third condition occurs withinsaid second predetermined time period.
 2. A system according to claim 1wherein the first timer is arranged to start timing in response toinitiation of feeding movement of a workpiece by the machine and timingby the first timer is arrested in response to contact of said workpiecewith a sensing element of the sensing means.
 3. A system according toclaim 1 wherein the second timer is arranged to start timing in responseto contact of a workpiece fed by the machine with a sensing element ofthe sensing means and timing by the second timer is arrested in responseto disengagement of said workpiece from said sensing element.
 4. Asystem according to claim 1 wherein said machine includes means forfeeding a workpiece through a predeteRmined distance within said firstpredetermined time period and means for performing an operation of saidworkpiece on completion of feeding thereof through said predetermineddistance, completion of feeding of said workpiece through saidpredetermined distance constituting said second given operatingcondition of the machine, said system further including further sensingmeans for sensing feed movement of said workpiece in excess of saidpredetermined distance by a pre-selected amount and actuating saidmodifying means in response to sensing of said excess feed movement. 5.A system according to claim 1 wherein the modifying means actuated byeach timer interrupts the machine feed at the end of the period at whichthe timer is set to time.
 6. A sensing and control system forcontrolling the operation of a machine comprising a timer arranged toactuate means to modify the action of the machine after the elapse of apredetermined time period from the occurrence of a first given operatingcondition of the machine if a second given operating condition of themachine does not occur before said time period elapses, includingsensing means for detecting the occurrence of said second operatingcondition and preventing actuation of said modifying means by the timerwhen said second condition is detected during said predetermined timeperiod, said machine including means for feeding a workpiece through apredetermined distance within said predetermined time period, completionof feeding of said workpiece through said predetermined distanceconstituting said second given operating condition of the machine, saidsystem further including sensing means for sensing feed movement of saidworkpiece in excess of said predetermined distance by a pre-selectedamount and actuating said modifying means in response to sensing of saidexcess movement.